Human serum albumin (hereafter albumin) is the most abundant protein in human blood plasma. Circulating albumin is a 585 amino acid protein with a molecular weight of 67 kDa. The protein has a serum half-life of about 20 days and is involved in transporting many hormones, metabolites, and drugs as well as maintaining oncotic pressure and buffering blood pH. Albumin is therapeutically administered to replace lost fluid and restore blood volume in trauma, burn, and surgery patients.
Cohn first described the purification of albumin from human plasma through differential fractionation. See Cohn et al., J. Am. Chem. Soc. 68: 459-475 (1946); Cohn et al., J. Am. Chem. Soc. 69: 1753-1761 (1947); U.S. Pat. Nos. 2,390,074 and 2,469,193. These methods were improved by Gerlough. See U.S. Pat. Nos. 2,710,293 and 2,710,294. Such methods use cold ethanol and the manipulation of pH, ionic strength, protein concentration, and temperature to precipitate plasma proteins such as albumins.
The procedure for purifying albumin from human plasma for pharmaceutical products typically includes a viral inactivation step to reduce the risk of transmitting blood-borne viruses. These viral inactivation steps can include heat pasteurization, organic solvents, or combinations of organic solvents and detergents (e.g., tri-n-butyl phosphate and polysorbate 80). In addition, the fatty acid caprylate, or salt thereof (e.g., sodium caprylate), has been effectively used as a viral inactivation agent. See U.S. Pat. No. 4,939,176; International Patent Application Publication Nos. WO 1998/024485 and WO 2000/056768; Lundblad and Seng, Vox Sang. 60:75-81 (1991); Johnston, Jonstone, & Wu, Biologicals 31: 213-221 (2003). Further, caprylate has also been used as a stabilizing agent and as a partitioning agent in the purification of therapeutic human albumin. See U.S. Pat. Nos. 5,250,663 and 5,561,115.
Human albumin is purified from the Cohn Fraction IV-1 Effluent or Fraction V and includes an acetone drying step to concentrate the albumin and inactivate viruses. The acetone process is expensive and uses large quantities of acetone, which creates a fire or explosion hazard. Accordingly, alternative viral inactivation and concentration procedures are desirable. A method for purifying albumin from human plasma using caprylate viral inactivation under conditions of low pH and elevated temperature followed by ultrafiltration/diafiltration is described herein.